CVE-2021-4356 in Frontend File Manager Plugin
Summary
by MITRE • 06/07/2023
The Frontend File Manager plugin for WordPress is vulnerable to Unauthenticated Arbitrary File Download in versions up to, and including, 18.2. This is due to lacking authentication protections, capability checks, and sanitization, all on the wpfm_file_meta_update AJAX action. This makes it possible for unauthenticated attackers to download arbitrary files on the site, potentially leading to site takeover.
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Analysis
by VulDB Data Team • 07/05/2023
The Frontend File Manager plugin for WordPress represents a critical security vulnerability that affects versions up to and including 18.2, where an unauthenticated arbitrary file download flaw exists within the wpfm_file_meta_update AJAX action. This vulnerability stems from the absence of proper authentication mechanisms, capability checks, and input sanitization measures that should normally protect such sensitive operations. The flaw allows malicious actors to bypass normal access controls and directly request files from the server without requiring valid credentials or administrative privileges. This represents a fundamental breakdown in the plugin's security architecture, as it fails to implement basic security controls that are standard practice in web application development. The vulnerability operates at the core of WordPress's AJAX handling system, where legitimate administrative functions are exposed through endpoints that should be protected from unauthorized access.
The technical exploitation of this vulnerability occurs through the wpfm_file_meta_update AJAX action which lacks proper validation of user credentials and authorization status. Attackers can craft malicious requests that target specific file paths on the server, potentially accessing sensitive files such as wp-config.php, database credentials, plugin files, or even user data. Without proper sanitization of input parameters, attackers can manipulate file paths to traverse directories and access files outside of intended boundaries. This vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal attacks. The lack of authentication protections means that any visitor to the website can exploit this flaw, making it particularly dangerous as it requires no prior access or credentials to execute. The vulnerability demonstrates poor security design principles where administrative functions are exposed without proper access controls, violating the principle of least privilege that should govern all web application components.
The operational impact of this vulnerability extends far beyond simple file access, as it can lead to complete system compromise and site takeover. When attackers can download arbitrary files, they gain access to critical system information that can be used to escalate privileges, extract sensitive data, or deploy malicious code. The potential for credential exposure through wp-config.php or other configuration files can provide attackers with database access and administrative privileges across the entire WordPress installation. This vulnerability can be exploited to download plugin files, theme files, or core WordPress files, enabling attackers to analyze the system for additional vulnerabilities or to modify system behavior. The implications include data breaches, service disruption, and potential compromise of the entire hosting environment. From an attacker's perspective, this vulnerability represents a high-value target within the ATT&CK framework under the T1078 technique for Valid Accounts and T1083 for File and Directory Discovery, as it enables both unauthorized access and information gathering.
Mitigation strategies for this vulnerability must address both immediate remediation and long-term security improvements. The most effective immediate solution involves updating to the patched version of the Frontend File Manager plugin, which should include proper authentication checks and input sanitization. Administrators should also implement additional security measures such as restricting access to AJAX endpoints through .htaccess rules or firewall configurations, implementing rate limiting to prevent abuse, and monitoring for suspicious file download patterns. The plugin should be configured to require proper authentication for all administrative functions, and all input parameters should undergo strict validation and sanitization before processing. Security monitoring should be enhanced to detect unusual file access patterns, particularly those involving sensitive system files or configuration data. Organizations should also consider implementing web application firewalls that can detect and block malicious AJAX requests targeting known vulnerable endpoints. Regular security audits and penetration testing should be conducted to identify similar vulnerabilities in other plugins or themes, ensuring comprehensive protection against similar attack vectors that could compromise the overall security posture of WordPress installations.